The realization of grounded active RC multiport networks with a minimum number of capacitors

Applying a state-space technique and the reactance extraction principle in the realization of multiport network functions by means of grounded active RC networks containing grounded voltage-controlled voltage sources (VCVSs) and using a minimum number of grounded capacitors, a new theorem concerning the least upper bound on the number of grounded VCVSs sufficient for the realization is proved. The obtained expression for the least upper bound allows one to generate the least upper bound on the number of VCVSs sufficient to realize each of all possible different types of multiport network functions.The proof of the theorem is based upon the use of results concerning the number of VCVSs sufficient and, in general, necessary to realize an arbitrary real multiport network function by means of grounded active resistive multiport networks embedding grounded VCVSs, and on the results concerning the possibility of choosing a convenient equivalent minimal system realization.     

Solution of transients in active four-terminal networks

Matrix and operational methods together provide a compact, convenient and systematic solution of transients. This paper illustrates the application of these methods to the solution of active four-terminal networks. First, the matrices are written with the Laplacian operator, s, as the parameter. Second, the vacuum tube as a four-terminal network is reviewed. Third, an example is given which illustrates the use of the method.     

Mining user interests over active topics on social networks

Inferring users’ interests from their activities on social networks has been an emerging research topic in the recent years. Most existing approaches heavily rely on the explicit contributions (posts) of a user and overlook users’ implicit interests, i.e., those potential user interests that the user did not explicitly mention but might have interest in. Given a set of active topics present in a social network in a specified time interval, our goal is to build an interest profile for a user over these topics by considering both explicit and implicit interests of the user. The reason for this is that the interests of free-riders and cold start users who constitute a large majority of social network users, cannot be directly identified from their explicit contributions to the social network. Specifically, to infer users’ implicit interests, we propose a graph-based link prediction schema that operates over a representation model consisting of three types of information: user explicit contributions to topics, relationships between users, and the relatedness between topics. Through extensive experiments on different variants of our representation model and considering both homogeneous and heterogeneous link prediction, we investigate how topic relatedness and users’ homophily relation impact the quality of inferring users’ implicit interests. Comparison with state-of-the-art baselines on a real-world Twitter dataset demonstrates the effectiveness of our model in inferring users’ interests in terms of perplexity and in the context of retweet prediction application. Moreover, we further show that the impact of our work is especially meaningful when considered in case of free-riders and cold start users.     

FRP复合材料加固混凝土结构新技术研究进展

近十多年来，国内外对FRP加固(包括改造、修复)混凝土结构这一新技术进行了广泛的试验和理论研究，简要论述了这一新技术的研究进展，着重论述受弯构件加固后的破坏形式和承载力计算方法，包括梁的抗弯加固、梁的抗剪加固和板的抗弯加固等，供实际工程应用参考。     

对RC电路的讨论

一阶RC电路，时间常数τ和电容上的电压的表达式是经常所求量。本文采用举实例的方法讨论了R值为正，值为0，值为负的三种情况，并画电容上电压波形加深对过渡过程的理解。重点讨论了τ值为负以及对应电容上电压的表达式该如何理解，指出了理论指导实践的意义。     

Universal Active RC Networks

This paper presents two active RC networks—one containing finite-gain amplifiers and the other being the differential amplifier version—each of which can be used to realize the ratio of arbitrary polynomials in s as any of the following five two-port parameters: Voltage transfer function, driving-point admittance, transfer admittance, transfer impedance, current transfer function.     

工业废物最小化管理研究

本从废物最小化的发展过程出发，研究了废物最小化的内涵，废物最小化的层级和技术路径，探讨了实现废物最小化的基本途径，在此基础上，运用经济学式本原理探讨了废物最小化途径的经济特性和废物最小化的测算方法。最后，探讨了推广废物最小化这一环保模式的各种影响因素，试图通过工业生产流程，工艺的创新为我国工业化的升级换代以持续发展寻找一条切实可行而又经济的途径。     

A risk minimization framework for information retrieval

This paper presents a probabilistic information retrieval framework in which the retrieval problem is formally treated as a statistical decision problem. In this framework, queries and documents are modeled using statistical language models, user preferences are modeled through loss functions, and retrieval is cast as a risk minimization problem. We discuss how this framework can unify existing retrieval models and accommodate systematic development of new retrieval models. As an example of using the framework to model non-traditional retrieval problems, we derive retrieval models for subtopic retrieval, which is concerned with retrieving documents to cover many different subtopics of a general query topic. These new models differ from traditional retrieval models in that they relax the traditional assumption of independent relevance of documents.     

Interior point penalty functions for constrained minimization

A family of interior point penalty methods for constrained minimization problems are presented and such properties as accuracy and stability of the methods are discussed. A numerical example illustrating the theoretical results is given. Finally some practical guidelines as to which penalty method to apply are presented.     

Subspace-based spectrum estimation in innovation models by mixed norm minimization

In this paper, identification of discrete-time power spectra of multi-input/multi-output (MIMO) systems in innovation models from output-only time-domain measurements is considered.A hybrid identification algorithm unifying mixed norm minimization with subspace estimation method is proposed. The proposed algorithm first estimates a covariance matrix from measurements. A significant dimension reduction is achieved in this step. Next, a regularized nuclear norm optimization problem is solved to enforce sparsity on the selection of most parsimonious model structure. A modification of the covariance estimates in the proposed algorithm generates yet another algorithm capable of handling data records with sequentially and intermittently missing values. The new and the modified identification algorithms are tested on a numerical study and a real-life application example concerned with the estimation of joint power spectral density (PSD) of parallel road tracks.     

Sensitivity reduction in modal control systems

The conventional modal control theory is concerned with the problem of determining a state feedback matrix-valued gain which drives the system eigenvalues to prescribed positions. When the parameters of the open-loop system involve certain variations, the closed-loop eigenvalues, obtained by using a feedback gain determined as above, also contain variations. In the present paper the problem of choosing an additional state feedback gain such as to reduce the closed-loop eigenvalue variations as much as desired is solved. Specifically, upon the assumption that a nominal set of parameter values is given, and that a feedback modal control law which drives the eigenvalues of the nominal closed-loop system to the desired positions is known, two alternative expressions for the required additional reduced eigenvalue sensitivity feedback controller are derived. Both cases of known and unknown system state vector are considered. The theory is illustrated by several examples.     

神经网络在混凝土结构可靠度评估中的应用

由于混凝土结构股役期间大量不确定因素的影响，有时难以利用确定性函数或专家系统计算结构的性能退化。本文利用有限的样本建立并训练BP神经网络，推广出混凝土结构抗力的时变规律，并应用混凝土结构时变可靠度评估中，计算简单，精度高。     

复杂网络理论在组织网络研究中的应用

本文通过分析复杂网络的结构特征及其内在嵌入性机理,回顾了复杂网络的基本理论现状。然后,分析得到了组织网络的非线性、多模块特征,发现了组织网络与复杂网络共同的行为模式。据此,将复杂网络引入到组织网络的研究中来,分别从组织网络的表示方法与分析手段,组织网络的互动关系和程度对其鲁棒性和适应性的影响,组织网络内在的协调机理,以及其局部互动与全局演化动力学特征之间的关系等几个方面探讨了复杂网络理论在组织网络研究中的应用前景。     

Brokerage in SME networks

This study focuses on SME networks of design and high-tech companies in Southeast Netherlands. By highlighting the personal networks of members across design and high-tech industries, the study attempts to identify the main brokers in this dynamic environment. In addition, we investigate whether specific characteristics are associated with these brokers. The main contribution of the paper lies in the fact that, in contrast to most other work, it is of a quantitative nature and focuses on brokers identified in an actual network. Studying the phenomenon of brokerage provides us with clear insights into the concept of brokerage regarding SME networks in different fields. In particular we highlight how third parties contribute to the transfer and development of knowledge. Empirical results show, among others, that the most influential brokers are found in the non-profit and science sector and have a long track record in their branch.     

Order reduction of linear systems using an error minimization technique

A simple method is proposed for order reduction of linear continuous systems with real distinct eigenvalues. The steady state parts of the unit step responses of the original and reduced-order models are matched in this method. Zeros are synthesized by minimizing the error between the transient responses, where as dominant poles are retained. An example is solved to illustrate the superiority of the method over some existing ones.     

Cell structure minimization for incompletely specified cellular arrays of ROMs

Two new reduction techniques are presented for detecting equivalencies and redundancies in a given cellular array of ROMs and simplifying the cell structure. One of these techniques is related to the procedures for minimizing states in incompletely specified sequential machines.The first new procedure is developed as an extension of Biswas' procedure for minimizing the number of equivalent states and lateral signals. This generalized procedure applies to all classes of cellular arrays. The second reduction technique provides methods of detecting co-redundant states or lateral signals. This procedure is also generalized to apply to the more complex classes of cellular arrays. An illustrative example of each is included.     

On firm growth in networks

This paper is explorative in nature. Based on an empirical analysis of two different industrial settings (life sciences, LS; information and communication technologies, ICT), it investigates network growth and firm growth in networks. We find a remarkable correspondence between a few fundamental findings of the ‘old’ stochastic approach to the analysis of firm internal growth, and empirically observed patterns of firm external growth through collaborative agreements. We show that scale-free behavior in real-world industrial networks can be accounted for by a general and parsimonious model, originally developed by Herbert Simon in 1955, based on entry and proportional growth. However, relevant departures from the stochastic benchmark are revealed that cannot be ascribed to the effect of mergers and acquisitions (M&As) and growth autocorrelation. Moreover, different regimes of growth are found to be at work in the life sciences for originators versus developers of new business opportunities, reflecting the fact that growth is driven by specialization and division of labor in the processes of generation and attraction/development of technological opportunities.     

Pole sensitivity in coupling networks

When designing lossless networks, one is faced with the problem of choosing a zero configuration for the reflection coefficient ?(s). Bode showed that if parasitic capacitances are present as well as for power transfer optimization, the best zero configuration is to locate all of them in the left half-plane. Recently, Bode's result was generalized to include parasitic immitances at both ends (source and load) of the quadripole.This work adds a new result to the theory by looking at the overall transfer function poles. It is shown that (a) if the source resistance varies, one should select left half-plane zeros for ?(s); and (b) if the load impedance varies, one should select right half-plane zeros.The pole sensitivity criterion used is the distance between the actual transfer function poles and the poles of the ideal transfer function.     

Knowledge management in SME networks

The objective of this paper is to investigate the role of knowledge management (KM) in networks participated by small firms. To achieve this objective, the literature on KM in small firms has been reviewed. A research question has been defined and addressed through a questionnaire survey conducted in a small firms network. The findings indicate that the surveyed companies perceive the strategic value of KM and adopt several systems even if its adoption is constrained by a number of barriers. The results suggest that firms investigated need to adopt advanced KM systems to manage knowledge more effectively at network level. The evidences also indicate that the surveyed firms are willing to adopt a platform supporting the sharing and exchange of knowledge in the network with a positive impact on innovation processes and the exploitation of market opportunities. The paper outlines some managerial implications as well as avenues for further research.     

Finite-time dynamic coverage for mobile sensor networks in unknown environments using neural networks

This paper addresses the finite-time dynamic coverage problem for mobile sensor networks in unknown environments. By introducing a condition where dynamic coverage of all points within the sensing range of each sensor exceeds the desired coverage level by a positive constant, a switching control strategy is developed to guarantee the achievement of desired coverage of the whole mission domain in finite time. The environment is modeled by a density function and neural networks are introduced to learn the function. Due to the approximation capability of neural networks, the proposed control scheme can learn the environment without a priori knowledge on the structure of the density function.